The present invention relates to adhesive tapes and containers. More particularly, the present invention relates to adhesive tapes for closing containers and containers having closing tape.
Containers, such as bags and other packages, must be securely closed to contain their contents. The container must remain closed during storage and shipping and must withstand vibrations and shocks of rough handling. When distribution is complete, the consumer or end-user needs to open the container to remove the contents. Ideally, a container can be opened without tools or special skills. Achieving both secure closure and easy opening is difficult; many containers can be secure for shipment but are difficult to open. For example, multiple wall paper bags of dog food or fertilizer often have sewn tops which remain closed during shipping but are difficult for the end-user to open without tools or without damaging the bag and spilling unused contents.
U.S. Pat. No. 4,781,296 discloses making a Tyvek(copyright) spun-bonded olefin envelope openable. It improves upon the common paperboard envelopes which are relatively easy to open using conventional tearable tape strip tape products. This highly tear-resistant envelope material can be fused by ultrasonic sealing, creating lines of weakness. European Patent 447209 discloses an improved opening for Tyvek(copyright) envelopes. It uses reinforced strapping tape (or similar tape) which is nicked on the ends to control the direction of the tear through the envelope. It also includes cutting through the Tyvek(copyright) material, rather than just weakening it. These patents describe opening devices for light-weight mailing envelopes: they function well in this light weight application but are not readily usable to resist splitting when used on a heavier package because the tape is relatively easy to tear.
European Patent 755868 discloses a paperboard envelope using a single tape to close and open the envelope. A uniaxially-oriented plastic film is adhesive-coated on both sides, allowing it to function as a closing tape as well as an opening tape. The tape is nicked to control the direction of tear. The paperboard material of the envelope provides the tear resistance.
The Minnesota Mining and Manufacturing Company (3M) has sold tear strip tapes for many years. One version of tear strip tape (3M #8612 tape) has a polyethylene terephthalate (PET) backing and a reinforcing filament of polyester yarn or fiberglass coated with a pressure sensitive adhesive (PSA). This tape is applied to the inside of a corrugated box or to the inside of a paperboard mailing envelope. The corrugated board or paperboard is nicked on the outside of the tear strip to provide a tab which the end-user can pull. During opening, the tape remains intact and is not split. The tape pulls and tears through the corrugated board or paperboard. This tear strip tape can only be used in light-weight situations because the force required to tear the tape is relatively low. Other versions use a tensilized polypropylene tape with a PSA and, optionally, a reinforced strapping tape. These types of tear strips can also be applied to the adhesive side of a wider film tape such as a box sealing tape or a heat shrinkable tape. Again, the wide tape is nicked to provide a tab and to initiate tearing. The distance between nicks is wider than the tear strip. This is only used for lightweight packages because the nicks tend to propagate prematurely during shipping, if used on a heavier shipping container. Using this kind of conventional tear strip on a linear low density polyethylene (LLDPE) tape backing would not function because the tear strength and the elongation of the LLDPE is too high.
Lightweight film tear strip (with a PSA or with a heat-activated adhesive) is also applied to film overwraps on packages. One example is a pack of cigarettes.
A container for storing items has a flap for closing the container. The flap has first and second major surfaces and is formed of a tear resistant film material. The container includes means for adhering the first major surface of the flap to the container to close the container and a tearable tape strip. The tape strip is located on one of the first and second major surfaces of the flap, and permits tearing of itself and the flap with a given force notwithstanding that the tear resistant film flap is otherwise not cleanly tearable.
The tearable tape strip can be located on the first major surface of the flap such that tearing the tearable tape strip tears through the flap. The means for adhering the first major surface of the flap to the container can include an adhesive on at least part of the first major side of the flap, the container, or both.
In another embodiment, a tape for use in closing a container having opposing ends includes a base layer and a tearable tape strip. The base layer includes a tear resistant backing having a first side and a second side, and an adhesive on at least part of the first side of the backing. The tearable tape strip is located on the first side of the backing and has a first side and a second side. The tearable tape strip permits tearing of itself and the tear resistant backing with a given force notwithstanding that the tear resistant backing is otherwise not cleanly tearable. The adhesive can be located between the backing and the tearable tape strip and the tearable tape strip tears through the base layer when the tape is removed from the container.
The tear resistant backing can be LLDPE, low density polyethylene LDPE, cast polypropylene, and Kraton/polypropylene blends. The tearable tape strip can be one of reinforced strapping tape, tensilized polypropylene, and filament reinforced tape. The tearable tape strip can have at least one of filaments and ribs.
The tape can include a tab at one end. The tab is formed by nicks extending from at least one of the ends of the tape and is located at least partially through the tearable tape strip which facilitate beginning tears. In one version, at least one nick has a first portion and a second portion. The first portion extends from at least one of the ends of the tape and passes through only the base layer and the second portion passes through the tearable tape strip. This allows the tab to adhere to the container to reduce the risk of the container opening before the proper time.
The tape can include a means for indicating whether the container has been opened and reclosed. Using linear low density polyethylene as the tear resistant backing causes the torn edge of the tape to be distorted such that recovering the opened tape is noticeable even when covered with additional tape.